Web pages displayed at a user's device are expected to offer smooth interaction with minimal delay in rendering. That is, web pages should not only load quickly, but also run well. Further, a user should be able to scroll a web page without experiencing jitters to breaks in viewing experience. Most devices today refresh their screens 60 times a second. If the web page being displayed contains an animation or a transition, or the user is scrolling the pages, the browser needs to match the device's refresh rate and put up 1 new picture, or frame, for each of those screen refreshes. Thus, each frame has a budget of about 16 ms (1 second/60=16.67 ms). When a user's device fails to meet this budget (for example, when the processing speed of the device is slow), the frame rate drops, and the content judders on screen. This is often referred to as jank, and it negatively impacts the user's experience.
The techniques introduced here may be better understood by referring to the following Detailed Description in conjunction with the accompanying drawings, in which like reference numerals indicate identical or functionally similar elements.